Many fluid products are utilized by atomizing them into a mist consisting of a multitude of fine fluid droplets. This atomization process is frequently accomplished by providing a source of pressurized fluid and a nozzle through which the pressurized fluid is directed. The source of pressurized fluid can be provided, for example, by a manually actuated pump or by a pressurized container wherein the pressurization may be provided by a propellant which is soluble in the fluid, an atmospheric gas, or other form of pressurization. Upon exiting from the nozzle through one or more orifices, the fluid stream is broken apart into many small, airborne droplets. The fluid product may then be utilized in the form of an airborne cloud or fog, or more commonly the fluid product in atomized form is directed toward a surface to be coated with the product.
Atomizer nozzles may take many forms, including, for example, pressure-swirl nozzles which expel the product in an expanding, swirling hollow cone of fluid which breaks up or shears into fine fluid particles, impingement-type nozzles which impinge two or more streams of product to disintegrate the fluid into fine particles, and other types as well.
Many fluid products exhibit a tendency to solidify or dry out when exposed to atmospheric air, leaving behind a film or layer of dried product on any surface which was initially wetted with product in liquid form. While this may be a desirable characteristic on certain receiving surfaces, such a dried film or layer typically has a negative impact when the surface is the interior of a fluid passage or a nozzle orifice. A dried film or layer of product on the walls of a passage or the sides of a nozzle orifice will tend to narrow the passage or orifice, particularly as the build-up increases over time. Such a buildup often results in an uneven, roughened surface which tends to increase the rate of build-up.
Atomizer nozzles are particularly susceptible to build-up of dried product, as the nozzle passages and orifices are comparatively small and have dimensions which are critical to producing the desired spray pattern. As the surfaces of the nozzle passages and orifices become coated with dried product accumulated between dispensing operations, the spray pattern produced typically becomes more irregular and has larger and more unevenly-sized fluid particles. The fluid may emerge in large droplets, or even a solid stream of un-atomized liquid product. Eventually, if the build-up is severe enough, fluid flow through the nozzle may become completely obstructed, and the nozzle will cease to function.
Over the years, many attempts have been made to address the clogging of atomizer nozzles. Most rely upon mechanical means, such as moveable pins, sleeves, or scrapers to either seal the nozzle from the atmosphere (thus preventing drying of un-dispensed product) or to mechanically clear dried product from the nozzle orifice(s) or passages.
Such devices require additional parts, frequently moveable, which adds to the complexity and cost of the resulting nozzle, as well as poor aesthetic qualities. Particularly in today's era of mass-production, molded plastic parts, additional elements which must be separately molded and assembled are of particular concern.
Accordingly, it would be desirable to provide an atomizer nozzle which would exhibit a reduced tendency to clog with dried product residue, yet be economical to produce and reliable in service.